An ultrasonic receiver can be used to determine its location with reference to one or more ultrasonic emitters, such as locating a mobile device having an ultrasonic receiver and being present within a retail, factory, warehouse, or other indoor environment, for example. Fixed ultrasonic emitter(s) can transmit ultrasonic energy in a short burst which can be received by an ultrasonic transducer (audio microphone) in the ultrasonic receiver. The use of several ultrasonic emitters distributed within the environment can be used to provide a specific location of a particular device using techniques known in the art such as measuring time-of-flight or signal strength of the emitter signals and using triangulation, trilateration, and the like, as have been used in radio frequency locationing systems.
However, ultrasonic emitters may not always be in the line-of-sight of the mobile device, and typical emitter signals may not be strong enough to directly penetrate through obstacles (herein referred to as attenuators) very well, such that reflected signals may reach the mobile device better than a direct signal from the emitter. This leads to inaccurate locationing results. In addition, having many mobile devices trying to establish their position within the environment, and interacting with all the emitters in the environment cannot be done simultaneously since separate emitter signals would interfere with each other, which results in a poor position update rate.
One solution for locationing uses time-slicing, where each emitter can send its ultrasonic burst and then wait for any reflected echoes to settle before the subsequent ultrasonic bursts are sent by that or other emitters. This technique solves the interference problem, but still results in a poor update rate since each emitter can only send its burst after a relatively long time. This technique also does not resolve the non-line-of-sight inaccuracy issue.
Another solution for locationing could use more ultrasonic bandwidth, where a larger range of ultrasonic frequencies can be used. However, today's mobile devices have a very limited ability to hear ultrasonic frequencies, typically between 19-22 kHz. Therefore, the only way to expand usable bandwidth would be to replace the existing audio circuitry of the mobile device to operate on higher frequencies, which is cost prohibitive. Alternatively, the usable frequencies could be expanded down into the audio range, but this would become disruptive to the users.
Accordingly, there is a need for a technique to locate a mobile device in an indoor environment while eliminating the aforementioned issues. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing background.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.